Mortgage Servicing Rights and Related Liabilities - UPB related to owned MSRs (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	$ 678,112	$ 587,942
Fair Value	10,035	9,090
Forward MSRs Sold, Subservicing Retained
Owned Service Loans [Line Items]
UPB	7,319		$ 22,640
Agency | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	652,901	561,656
Fair Value	9,686	8,774
Non-agency | Mortgage servicing rights
Owned Service Loans [Line Items]
UPB	25,211	26,286
Fair Value	$ 349	$ 316